1. Field of the Invention
This invention relates to an input device of the tablet type wherein in response to pushing of a given location on a tablet serving as an input board by the use of a push pen the positional information of the pushed location is entered.
2. Description of the Prior Art
Hitherto, various types of input devices, such as the key input type or tablet input type, are connected to and used with microcomputers, such as personal computers or TV game sets, in compliance with the purpose of use.
FIGS. 3 through 6 show an example of the tablet type input device. The illustrated input device comprises opposed lower planar resistance body and upper planar resistance body with a plurality of dot spacers interposed therebetween which are distributed substantially over the whole face, and is designed so that as any desired point is pushed from the external thereby these resistance bodies becoming into contact with each other a variation of potential at that contacted point is detected and entered in terms of the positional information.
Describing more clearly, in FIG. 3, 1 is a fixed plate of square shape, and 1A is a lead-wire outgoing section. As shown in FIG. 4, on the fixed plate 1 there are piled one upon another a lower insulating member 2, lower planar resistance body 3, dot spacers 4, 4, . . . , upper planar resistance body 5, and upper insulating member 6, in this order as viewed from the bottom upward.
As shown in FIG. 3, on the lower planar resistance body 3 terminal electrodes 7 and 8 of strip shape are provided on the sides thereof. 7A and 8A are lead wires of the terminal electrodes 7 and 8, respectively. On the outside of these terminal electrodes 7 and 8 an earth electrode 9 for prevention of entrance of noise is provided so as to surround the whole of the lower planar resistance body 3. 9A is a lead wire of the earth electrode 9 and 6A is a protection sheet.
Similarly to the lower planar resistance body 3, at respective vertical marginal portions in FIG. 3 of the upper planar resistance body 5 laterally-extending terminal electrodes (not shown) of strip shape are provided, and their lead wires 17A and 18A are led outward through the lead-wire outgoing section 1A. In this body 5, also, an earth electrode (not shown) similar to the earth electrode 9 is provided on the outside of the terminal electrodes.
Each of these insulating members 2, 6 and planar resistance bodies 3, 5 is made by soft material having elasticity, the lower planar resistance body 3 is secured integrally to the lower insulating member 2, and the upper planar resistance body 5 is secured integrally to the upper insulating member 6.
In operation of the input device, a given location on the tablet of the foregoing configuration is pushed by a push pen 10, as shown in FIG. 5. As the result of pushing, the upper resistance body 5 is bent together with the upper insulating member 6 to come into contact with the lower resistance body 3, as illustrated in the drawing. In this connection the device is designed so that respective variations of resistance between the terminal electrodes are measured while selecting each in accordance with a predetermined routine, whereby the location where the push pen 10 makes contact can be specified instantly.
In the conventional device of the table type described hereinabove, however, because a plurality of dot spacers 4, 4, . . . 4 print-molded by hard material such as silicon resin are arranged between the upper and lower planar resistance bodies 5 and 3, if the push pen 10 is made to abut on a spot above the dot spacer 4 as shown in FIG. 6, for example, the upper insulating member 6 does not bend and the planar resistance bodies 5 and 3 do not come into contact with each other really; thus each spot as above creates a so-called insensitive zone inconveniently. Further, because the upper insulating member 6 has a limitation in the extent of bend, the insensitive zone is comparatively large and there is the disadvantage that the resolution of the device as a whole can not be made high.